<!DOCTYPE html>
<html lang="en">
<body>
	<input name="button" type="button" id="button" value='Click me'
		disabled="disabled" />
	<script
		src="http://ajax.googleapis.com/ajax/libs/jquery/1.7.2/jquery.min.js"></script>
	<script>
		(function($) {
			$('#button').removeAttr('disabled');
			// or 
			// $('#button').attr('disabled', '');  
		})(jQuery);
	</script>
</body>
</html>